Power supply system

ABSTRACT

A control device of a power supply system includes a first processing unit and a second processing unit. The first processing unit is a processing unit configured to perform a first process of determining certain strings out of a plurality of strings connected in parallel to a power distribution device. The second processing unit is a processing unit configured to perform a second process of performing inputting of electric power to the plurality of strings connected in parallel to the power distribution device or outputting of electric power from the plurality of strings to the power distribution device using at least the certain strings determined by the first processing unit.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2018-223880 filed onNov. 29, 2018 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND 1. Technical Field

The disclosure relates to a power supply system.

2. Description of Related Art

A power supply system that includes a plurality of modules of which eachincludes a battery and a circuit and performs at least one of outputtingof electric power to the outside and storage of electric power which isinput from the outside by controlling the plurality of modules is known.For example, a power supply device (a power supply system) described inJapanese Patent Application Publication No. 2018-74709 (JP 2018-74709 A)includes a plurality of battery circuit modules of which each includes abattery, a first switching element, and a second switching element. Theplurality of battery circuit modules are connected in series with outputterminals interposed therebetween. A control circuit of the power supplydevice outputs a gate signal for switching the first switching elementand the second switching element between ON and OFF to the batterycircuit modules at intervals of a predetermined time. Accordingly, atarget electric power is output from the plurality of battery circuitmodules.

SUMMARY

The power supply device described in JP 2018-74709 A can be additionallyprovided with a device that detects a state of the power supply devicebased on a current value. When the state of the power supply device ismonitored using such a device and a current flowing in the power supplydevice is small, an error in the device that detects the state of thepower supply device based on a current value may increase and causemisunderstanding of the state of the power supply device. A plurality ofpower supply devices can be incorporated into a power distributiondevice connected to a power system to be parallel to each other.However, when a plurality of power supply devices is incorporated into apower distribution device to be parallel to each other and electricpower which is required by the power distribution device is small, acurrent flowing in one power supply device decreases. This may causemisunderstanding of the state of the power supply device.

According to an aspect of the disclosure, there is provided a powersupply system including: a power distribution device that is connectedto a power system; a plurality of strings that is connected in parallelto the power distribution device; and a control device. Each stringincludes a main line that is connected to the power distribution deviceand a plurality of sweep modules that is disposed along the main line.Each sweep module includes a battery module, an input and output circuitthat is configured to connect the battery module in series to the mainline, and at least one switching element that is provided in the inputand output circuit and is configured to switch between connection anddisconnection between the battery module and the main line. The controldevice is configured to control inputting of electric power from thepower system connected to the power distribution device to the pluralityof strings connected to the power distribution device and outputting ofelectric power from the plurality of strings to the power system. Thecontrol device is configured to perform a first process of determiningcertain strings out of the plurality of strings connected in parallel tothe power distribution device and a second process of performinginputting of electric power to the plurality of strings connected inparallel to the power distribution device or outputting electric powerfrom the plurality of strings to the power distribution device using atleast the certain strings.

With this power supply system, it is possible to stably easily secure acurrent value required for a string.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments will be described below with reference to theaccompanying drawings, in which like numerals denote like elements, andwherein:

FIG. 1 is a diagram schematically illustrating a configuration of apower supply system 1;

FIG. 2 is a diagram schematically illustrating a configuration of asweep module 20;

FIG. 3 is a timing chart illustrating an example of a sweep operation;

FIG. 4 is a timing chart illustrating an example of a forcible throughoperation;

FIG. 5 is a block diagram illustrating a control device 100 of the powersupply system 1; and

FIG. 6 is a flowchart illustrating an example of a first process and asecond process in the control device 100.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an exemplary embodiment of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Detailswhich are not particularly mentioned in this specification and which arerequired for embodiment can be understood as design details based on therelated art by those skilled in the art. The disclosure can be embodiedbased on details described in this specification and common generaltechnical knowledge in the art. In the following drawings, members andparts performing the same operations will be referred to by the samereference signs. The dimensional relationships in the drawings do notreflect actual dimensional relationships.

<Overall Schematic Configuration>

The overall configuration of a power supply system 1 according to anembodiment will be schematically described below with reference toFIG. 1. The power supply system 1 performs at least one of outputting ofelectric power to a power distribution device 5 which is connected to ahost power system 8 and storage of electric power which is input fromthe power distribution device 5 (hereinafter simply referred to as“inputting and outputting of electric power”). For example, in thisembodiment, a power conditioning subsystem (PCS) is used as the powerdistribution device 5. The PCS has a function of converting electricpower input from the power system 8 to the power supply system 1 or thelike and electric power output from the power supply system 1 or thelike to the power system 8 between the power supply system 1 or the likeand the power system 8.

When electric power is surplus to the power system 8, the powerdistribution device 5 outputs the surplus electric power to the powersupply system 1. In this case, the power supply system 1 stores electricpower which is input from the power distribution device 5. The powersupply system 1 outputs electric power stored in the power supply system1 to the power distribution device 5 in accordance with an instructionfrom a host system 6 that controls the host power system 8. In FIG. 1,the host system 6 is a system that controls the power system 8 and thepower distribution device 5 and is provided separately from the powersystem 8 and the power distribution device 5. However, the host system 6may be incorporated into the power system 8 or the power distributiondevice 5.

The power supply system 1 includes one or more strings 10. The powersupply system 1 according to this embodiment includes a plurality of (N:N 2) strings 10 (10A, 10B, . . . , 10N). In FIG. 1, for the purpose ofconvenience, only two strings 10A and 10B out of the N strings 10 areillustrated. Each string 10 serves as a unit for inputting andoutputting electric power to and from the power distribution device 5.The plurality of strings 10 is connected in parallel to the powerdistribution device 5. Inputting and outputting (supply of power) ofelectric power between the power distribution device 5 and each string10 is performed via a main line 7.

Each string 10 includes a string control unit (SCU) 11 and a pluralityof (M: M≥2) sweep modules 20 (20A, 20B, . . . , 20M). Each sweep module20 includes a battery and a control circuit. The SCU 11 is provided foreach string 10. The SCU 11 is a controller that comprehensively controlsthe plurality of sweep modules 20 included in the corresponding string10. Each SCU 11 communicates with a group control unit (GCU) 2 servingas a power control device. The GCU 2 is a controller thatcomprehensively controls a group including the plurality of strings 10as a whole. The GCU 2 communicates with the host system 6 and the SCUs11. Various methods (for example, at least one of wired communication,wireless communication, and communication via a network) can be employedas a method of communication between the host system 6, the GCU 2, andthe SCUs 11.

The configuration of the controllers that control the strings 10, thesweep modules 20, and the like may be modified. For example, the GCU 2and the SCUs 11 may not be separately provided. That is, one controllermay control the whole group including one or more strings 10 and all theplurality of sweep modules 20 included in the string 10.

<Sweep Module>

A sweep module 20 will be described below in detail with reference toFIG. 2. The sweep module 20 includes a battery module 30, a powercircuit module 40, and a sweep unit (SU) 50.

The battery module 30 includes at least one battery 31. A plurality ofbatteries 31 is provided in the battery module 30 according to thisembodiment. The plurality of batteries 31 is connected in series. Inthis embodiment, a secondary battery is used as each battery 31. Atleast one of various secondary batteries (for example, a nickel-hydridebattery, a lithium ion battery, and a nickel-cadmium battery) can beused as the battery 31. In the power supply system 1, a plurality oftypes of batteries 31 may be mixed. The types of the batteries 31 in allthe battery modules 30 may be the same.

A voltage detecting unit 35 and a temperature detecting unit 36 areprovided in the battery module 30. The voltage detecting unit 35 detectsa voltage of the batteries 31 in the battery module 30 (the plurality ofbatteries 31 connected in series in this embodiment). The temperaturedetecting unit 36 detects a temperature of the batteries 31 in thebattery module 30 or a temperature near the batteries 31. Variousdevices (for example, a thermistor) that detect a temperature can beused as the temperature detecting unit 36.

The battery module 30 is provided to be attached to and detached fromthe power circuit module 40. Specifically, in this embodiment, with thebattery module 30 including a plurality of batteries 31 as one unit,detachment of the battery module 30 from the power circuit module 40 andattachment thereof to the power circuit module 40 are performed.Accordingly, in comparison with a case in which the batteries 31 in thebattery module 30 are replaced one by one, the number of operation stepswhen an operator replaces the batteries 31 decreases. In thisembodiment, the voltage detecting unit 35 and the temperature detectingunit 36 are replaced separately from the battery module 30. However, atleast one of the voltage detecting unit 35 and the temperature detectingunit 36 may be replaced along with the battery module 30.

The power circuit module 40 forms a circuit for appropriately realizinginputting and outputting of electric power in the battery module 30. Inthis embodiment, the power circuit module 40 includes at least oneswitching element that switches between connection and disconnectionbetween the battery module 30 and the main line 7. In this embodiment,the power circuit module 40 includes an input and output circuit 43 thatconnects the battery module 30 to the main line 7 and a first switchingelement 41 and a second switching element 42 that are provided in theinput and output circuit 43. The first switching element 41 and thesecond switching element 42 perform a switching operation in accordancewith a signal (for example, a gate signal) which is input form the sweepunit 50.

In this embodiment, as illustrated in FIG. 2, the first switchingelement 41 is attached in series to the main line 7 and in parallel tothe battery module 30 in the input and output circuit 43. The secondswitching element 42 is attached to a part of the input and outputcircuit 43 that connects the battery module 30 in series to the mainline 7. A source and a drain of the first switching element 41 aredisposed such that a forward direction thereof is set to a direction inwhich a discharging current flows in the main line 7. A source and adrain of the second switching element 42 are disposed in the input andoutput circuit 43 attaching the battery module 30 in series to the mainline 7 such that a forward direction thereof is set to a direction inwhich a charging current flows in the battery module 30. In thisembodiment, the first switching element 41 and the second switchingelement 42 are MOSFETs (for example, Si-MOSFETs) and include body diodes41 a and 42 a, respectively, set to a forward direction. Here, the bodydiode 41 a of the first switching element 41 can be appropriatelyreferred to as a first body diode. The body diode 42 a of the secondswitching element 42 can be appropriately referred to as a second bodydiode.

The first switching element 41 and the second switching element 42 arenot limited to the example illustrated in FIG. 2. Various elements thatcan switch between connection and disconnection can be used as the firstswitching element 41 and the second switching element 42. In thisembodiment, a MOSFET (specifically an Si-MOSFET) is used as both thefirst switching element 41 and the second switching element 42. However,an element (for example, a transistor) other than a MOSFET may beemployed.

The power circuit module 40 includes an inductor 46 and a capacitor 47.The inductor 46 is provided between the battery module 30 and the secondswitching element 42. The capacitor 47 is connected in parallel to thebattery module 30. In this embodiment, since secondary batteries areused as the batteries 31 of the battery module 30, it is necessary tocurb deterioration of the batteries 31 due to an increase in internalresistance loss. Accordingly, by forming an RLC filter using the batterymodule 30, the inductor 46, and the capacitor 47, equalization of acurrent is achieved.

A temperature detecting unit 48 is provided in the power circuit module40. The temperature detecting unit 48 is provided to detect emission ofheat from at least one of the first switching element 41 and the secondswitching element 42. In this embodiment, the first switching element41, the second switching element 42, and the temperature detecting unit48 are assembled into one base. Accordingly, the base is replaced at atime point at which a defect of one of the first switching element 41and the second switching element 42 has been detected. Accordingly, inthis embodiment, by providing one temperature detecting unit 48 near thefirst switching element 41 and the second switching element 42, it ispossible to decrease the number of components. Here, a temperaturedetecting unit that detects the temperature of the first switchingelement 41 and a temperature detecting unit that detects the temperatureof the second switching element 42 may be provided separately from eachother. Various devices (for example, a thermistor) that detect atemperature can be used as the temperature detecting unit 48.

As illustrated in FIGS. 1 and 2, a plurality of battery modules 30 inthe string 10 are connected in series to the main line 7 with the powercircuit modules 40 interposed therebetween. By appropriately controllingthe first switching element 41 and the second switching element 42 ofeach power circuit module 40, the corresponding battery module 30 isconnected to the main line 7 or is disconnected from the main line 7. Inthe example of the configuration of the power circuit module 40illustrated in FIG. 2, when the first switching element 41 is turned offand the second switching element 42 is turned on, the battery module 30is connected to the main line 7. When the first switching element 41 isturned on and the second switching element 42 is turned off, the batterymodule 30 is disconnected from the main line 7.

The sweep unit (SU) 50 is a control unit that is incorporated into thesweep module 20 such that various controls associated with the sweepmodule 20 are executed, and is also referred to as a sweep control unit.Specifically, the sweep unit 50 outputs a signal for driving the firstswitching element 41 and the second switching element 42 in the powercircuit module 40. The sweep unit 50 notifies a host controller (the SCU11 illustrated in FIG. 1 in this embodiment) of states of the sweepmodule 20 (for example, the voltage of the battery module 30, thetemperature of the batteries 31, and the temperature of the switchingelements 41 and 42). The sweep unit 50 is incorporated into each of aplurality of sweep modules 20 of each string 10. The sweep units 50incorporated into the plurality of sweep modules 20 of each string 10are sequentially connected to each other and are configured to allow agate signal GS which is output from the SCU 11 to propagatesequentially. As illustrated in FIG. 2, in this embodiment, each sweepunit 50 includes an SU processing unit 51, a delay/selection circuit 52,and a gate driver 53.

The SU processing unit 51 is a controller that takes charge of variousprocesses in the sweep unit 50. For example, a microcomputer can be usedas the SU processing unit 51. Detection signals from the voltagedetecting unit 35, the temperature detecting unit 36, and thetemperature detecting unit 48 are input to the SU processing unit 51.The SU processing unit 51 performs inputting and outputting varioussignals to and from a host controller (the SCU 11 of the string 10 inthis embodiment).

The signals which are input from the SCU 11 to the SU processing unit 51include a forcible through signal CSS and a forcible connection signalCCS. The forcible through signal CSS is a signal for instructing todisconnect the battery module 30 from the main line 7 (see FIG. 1)extending from the power distribution device 5 to the string 10. Thatis, the sweep module 20 to which the forcible through signal CSS isinput ignores an operation for inputting and outputting electric powerto and from the power distribution device 5. The forcible connectionsignal CCS is a signal for instructing to maintain connection of thebattery module 30 to the main line 7.

A gate signal GS is input to the delay/selection circuit 52. The gatesignal (a PWM signal in this embodiment) GS is a signal for controllingan alternate repeated switching operation between an ON state and an OFFstate of the first switching element 41 and the second switching element42. The gate signal GS is a pulse-shaped signal in which ON and OFF arealternately repeated. The gate signal GS is first input to thedelay/selection circuit 52 in one sweep module 20 from the SCU 11 (seeFIG. 1). Subsequently, the gate signal GS propagates sequentially fromthe delay/selection circuit 52 of one sweep module 20 to thedelay/selection circuit 52 of another sweep module 20.

In each string 10, sweep control which is illustrated in FIGS. 3 and 4is executed. Here, FIG. 3 is a timing chart illustrating an example of asweep operation. Specifically, in FIG. 3, a relationship between aconnection state of the sweep modules 20 and a voltage output to thepower distribution device 5 when all the sweep modules 20 execute thesweep operation is illustrated as an example. FIG. 4 is a timing chartillustrating an example of a forcible through operation. Specifically,in FIG. 4, a relationship between a connection state of the sweepmodules 20 and a voltage output to the power distribution device 5 whencertain sweep modules 20 execute the forcible through operation isillustrated as an example.

In sweep control which is executed in each string 10, the number m ofsweep modules 20 which are turned on at the same time out of a pluralityof (for example, M) sweep modules 20 incorporated into the string 10 isdetermined. The gate signal GS in sweep control has, for example, apulse-shaped waveform. In the gate signal GS, for example, a signalwaveform for connecting the battery module 30 to the main line 7 and asignal waveform for disconnecting the battery module 30 from the mainline 7 may be sequentially disposed. In the gate signal GS, the signalwaveform for connecting the battery module 30 to the main line 7 mayembed the number of battery modules 30 which are connected to the mainline 7 in a predetermined period T in which the string 10 is swept. Thesignal waveform for disconnecting the battery module 30 from the mainline 7 may embed the number of battery modules 30 which are to bedisconnected from the main line 7 out of the battery modules 30incorporated into the string 10. In the signal waveform for connectingthe battery module 30 to the main line 7 and the signal waveform fordisconnecting the battery module 30 from the main line 7, wavelengthsthereof and the like are appropriately adjusted.

In each string 10 according to this embodiment, M sweep modules 20 areconnected in series in the order of sweep modules 20A, 20B, . . . , 20Mfrom the power distribution device 5. In the following description, aside which is close to the power distribution device 5 is defined as anupstream side, and a side which is distant from the power distributiondevice 5 is defined as a furthest downstream side. First, the gatesignal GS is input from the SCU 11 to the delay/selection circuit 52 ofthe sweep unit 50 in the sweep module 20A which is furthest upstream.Subsequently, the gate signal GS propagates from the delay/selectioncircuit 52 of the sweep module 20A to the delay/selection circuit 52 ofthe sweep module 20B adjacent thereto downstream. Propagation of thegate signal to the sweep module 20 adjacent thereto downstream issequentially repeated up to the sweep module 20M which is furthestdownstream.

Here, the delay/selection circuit 52 can allow a pulse-shaped gatesignal GS which is input from the SCU 11 or the upstream sweep module 20to propagate to the downstream sweep module 20 with a delay of apredetermined delay time. In this case, a signal indicating the delaytime is input from the SCU 11 to the sweep unit 50 (the SU processingunit 51 in the sweep unit 50 in this embodiment). The delay/selectioncircuit 52 delays the gate signal GS based on the delay time indicatedby the signal. The delay/selection circuit 52 may allow the input gatesignal GS to propagate to the downstream sweep module 20 without adelay.

The gate driver 53 drives the switching operations of the firstswitching element 41 and the second switching element 42. Thedelay/selection circuit 52 outputs a signal for controlling driving ofthe gate driver 53 to the gate driver 53. The gate driver 53 outputscontrol signals to the first switching element 41 and the secondswitching element 42. When the battery module 30 is to be connected tothe main line 7, the gate driver 53 outputs a control signal for turningoff the first switching element 41 and turning on the second switchingelement 42. When the battery module 30 is disconnected from the mainline 7, the gate driver 53 outputs a control signal for turning on thefirst switching element 41 and the turning off the second switchingelement 42.

The delay/selection circuit 52 in this embodiment is controlled by acontroller such as the SCU 11 and selectively performs a sweepoperation, a forcible through operation, and a forcible connectionoperation.

For example, in the sweep operation, the first switching element 41 andthe second switching element 42 are operated by the gate signal GS. Aplurality of battery modules 30 included in the string 10 are connectedto the main line 7 in a predetermined order and is disconnected from themain line 7 in a predetermined order. As a result, the string 10 isdriven such that a predetermined number of battery modules 30 arenormally connected to the main line 7 while sequentially changing thebattery modules 30 connected to the main line 7 in a short controlcycle. Through this sweep operation, the string 10 serves as one batterypack in which the predetermined number of battery modules 30 areconnected in series while sequentially changing the battery modules 30connected to the main line 7 in the short control cycle. The sweepmodules 20 of the string 10 are controlled by the SCU 11 such that sucha sweep operation is realized. In this control, the SCU 11 outputs thegate signal GS to the string 10 and outputs the control signal to the SUprocessing unit 51 incorporated into the sweep module 20. Details of anexample of the sweep operation will be described later with reference toFIGS. 3 and 4.

In the sweep operation, the delay/selection circuit 52 outputs the inputgate signal GS to the gate driver 53 without any change and causes thegate signal GS to propagate to a downstream sweep module 20 with a delayof a delay time. As a result, the battery modules 30 of the sweepmodules 20 under the sweep operation are sequentially connected to themain line 7 and are sequentially disconnected from the main line 7 atdifferent timings in the string 10.

In the forcible through operation, the delay/selection circuit 52outputs a signal for maintaining the first switching element 41 in theON state and maintaining the second switching element 42 in the OFFstate to the gate driver 53 regardless of the input gate signal GS. As aresult, the battery modules 30 of the sweep modules 20 under theforcible through operation are disconnected from the main line 7. Thedelay/selection circuit 52 of the sweep module 20 under the forciblethrough operation causes the gate signal GS to propagate the downstreamsweep module 20 without a delay.

In the forcible connection operation, the delay/selection circuit 52outputs a signal for maintaining the first switching element 41 in theOFF state and maintaining the second switching element 42 in the ONstate to the gate driver 53 regardless of the input gate signal GS. As aresult, the battery modules 30 of the sweep modules 20 under theforcible connection operation are normally connected to the main line 7.The delay/selection circuit 52 of the sweep module 20 under the forcibleconnection operation causes the gate signal GS to propagate thedownstream sweep module 20 without a delay.

The delay/selection circuit 52 may be constituted as a single integratedcircuit that performs the above-mentioned necessary functions. Thedelay/selection circuit 52 may be constituted in combination between acircuit that delays a gate signal GS and a circuit that selectivelyoutputs a gate signal GS to the gate driver 53. An example of theconfiguration of the delay/selection circuit 52 in this embodiment willbe described below.

In this embodiment, as illustrated in FIG. 2, the delay/selectioncircuit 52 includes a delay circuit 52 a and a selection circuit 52 b.The gate signal GS input to the delay/selection circuit 52 is input tothe delay circuit 52 a. The delay circuit 52 a outputs the gate signalGS to the selection circuit 52 b with a delay of a predetermined delaytime. The gate signal GS input to the delay/selection circuit 52 isoutput to the selection circuit 52 b via another route which does notpass through the delay circuit 52 a without any change. The selectioncircuit 52 b receives an instruction signal form the SU processing unit51 and outputs the gate signal GS in accordance with the instructionsignal.

When the instruction signal from the SU processing unit 51 instructs toperform a sweep operation, the selection circuit 52 b outputs the inputgate signal GS to the gate driver 53 of the sweep module 20 without anychange. The gate driver 53 outputs a control signal to the power circuitmodule 40, turns off the first switching element 41, turns on the secondswitching element 42, and connects the battery module 30 to the mainline 7. On the other hand, the selection circuit 52 b outputs the gatesignal GS with a delay to the delay/selection circuit 52 of the sweepmodule 20 adjacent thereto downstream. That is, when the battery module30 is connected to the main line 7 in the sweep operation, the gatesignal GS with a delay of a predetermined delay time is sent to thesweep module 20 adjacent thereto downstream.

When the instruction signal from the SU processing unit 51 is theforcible through signal CSS, the selection circuit 52 b outputs a signalfor ignoring the battery module 30 to the gate driver 53. By maintainingthe forcible through signal CSS, the battery module 30 of the sweepmodule 20 receiving the forcible through signal CSS is maintained in astate in which it is disconnected from the main line 7. In this case,the selection circuit 52 b outputs the gate signal GS, which is input tothe selection circuit 52 b via another route which does not pass throughthe delay circuit 52 a, to the sweep module 20 adjacent theretodownstream.

When the instruction signal from the SU processing unit 51 is theforcible connection signal CCS, the selection circuit 52 b outputs asignal for connecting the battery module 30 to the main line 7 to thegate driver 53. That is, the gate driver 53 turns off the firstswitching element 41, turns on the second switching element 42, andconnects the battery module 30 to the main line 7. By maintaining theforcible connection signal CCS, the battery module 30 is maintained in astate in which it is connected to the main line 7. In this case, theselection circuit 52 b outputs the gate signal GS, which is input to theselection circuit 52 b via another route which does not pass through thedelay circuit 52 a, to the sweep module 20 adjacent thereto downstream.

As illustrated in FIGS. 1 and 2, in this embodiment, a plurality ofsweep units 50 (specifically a plurality of delay/selection circuits 52)included in one string 10 is sequentially connected in a daisy chainmanner. As a result, the gate signal GS input form the SCU 11 to onesweep unit 50 propagates sequentially to the plurality of sweep units50. Accordingly, processes in the SCU 11 are likely to be simplified andan increase in signal properties is easily curbed. However, the SCU 11may individually output the gate signal GS to the plurality of sweepunits 50.

Each sweep unit 50 includes an indicator 57. The indicator 57 notifiesan operator of, for example, a state of the sweep module 20 including abattery module 30 or a power circuit module 40. The indicator 57 cannotify an operator, for example, that a defect in the battery module 30of the sweep module 20 (for example, failure or deterioration of thebatteries 31) has been detected (that is, the battery module 30 shouldbe replaced).

For example, an LED which is a kind of light emitting device is used asthe indicator 57 in this embodiment. However, a device (for example, adisplay) other than an LED may be used as the indicator 57. A device(for example, a speaker) that outputs voice may be used as the indicator57. The indicator 57 may notify an operator of the state of the sweepmodule 20 by driving an actuator (for example, a motor or a solenoid).The indicator 57 may be configured to indicate the state using differentmethods depending on the state of the sweep module 20.

In this embodiment, the operation of the indicator 57 is controlled bythe SU processing unit 51 of the sweep unit 50. However, a controller(for example, the SCU 11) other than the SU processing unit 51 maycontrol the operation of the indicator 57.

In this embodiment, the indicator 57 is provided for each sweep unit 50.Accordingly, an operator can easily identify the sweep module 20 ofwhich the state has been notified by the indicator 57 out of theplurality of sweep modules 20 which are arranged. However, theconfiguration of the indicator 57 may be modified. For example,separately from the indicator 57 disposed for each sweep unit 50 oralong with the indicator 57, a state notifying unit that notifies thestates of a plurality of sweep modules 20 in a bundle may be provided.In this case, for example, the state notifying unit may display thestates of the plurality of sweep modules 20 (for example, whether adefect has occurred) on one monitor.

<Sweep Control>

Sweep control which is executed in a string 10 will be described below.Here, sweep control is control for causing each battery module 30 of thestring 10 to perform a sweep operation. In sweep control which isexecuted in the string 10, the SCU 11 outputs a pulse-shaped gate signalGS. The switching elements 41 and 42 in a plurality of sweep modules 20of the string 10 are driven to switch appropriately between ON and OFF.As a result, connection of the battery module 30 to the main line 7 anddisconnection of the battery module 30 from the main line 7 are fastswitched to each other for each sweep module 20. In the string 10, thegate signal GS which is input to an X-th sweep module 20 from upstreamcan be delayed with respect to the gate signal GS which is input to an(X−1)-th sweep module 20. As a result, m (m<M) sweep modules 20connected to the main line 7 out of M sweep modules 20 in the string 10are sequentially switched. Accordingly, a plurality of battery modules30 included in the string 10 is connected to the main line 7 in apredetermined order and is disconnected from the main line in apredetermined order. A predetermined number of battery modules 30 can benormally connected to the main line 7. Through this sweep operation, thestring 10 serves as a single battery pack in which a predeterminednumber of battery modules 30 are connected in series.

FIG. 3 is a timing chart illustrating an example of a relationshipbetween connection states of sweep modules 20 and a voltage which isoutput to the power distribution device 5 when all the sweep modules 20included in the string 10 are caused to perform the sweep operation. Thenumber M of sweep modules 20 included in one string 10 can beappropriately changed. In the example illustrated in FIG. 3, five sweepmodules 20 are included in one string 10 and all of the five sweepmodules 20 are caused to perform the sweep operation.

In the example illustrated in FIG. 3, a VH command signal for setting avoltage VH [V] output to the power distribution device 5 to 100 V isinput to the SCU 11 of the string 10. The voltage Vmod [V] of thebattery module 30 in each sweep module 20 is 43.2 V. The delay time DL[μsec] by which a gate signal GS is delayed is appropriately setdepending on the specification required for the power supply system 1.The period T of the gate signal GS (that is, the period in which a sweepmodule 20 is connected and disconnected) has a value which is obtainedby multiplying the delay time DL by the number P of sweep modules 20(≤M) which are to perform the sweep operation. Accordingly, when thedelay time DL is set to be greater, the frequency of the gate signal GSbecomes lower. On the other hand, when the delay time DL is set to beless, the frequency of the gate signal GS becomes higher. In theexample, illustrated in FIG. 3, the delay time DL is set to 2.4 μsec.Accordingly, the period T of the gate signal GS is “2.4 μsec×5=12 μsec.”

In this embodiment, a battery module 30 of a sweep module 20 in whichthe first switching element 41 is turned off and the second switchingelement 42 is turned on is connected to the main line 7. That is, whenthe first switching element 41 is turned off and the second switchingelement 42 is turned on, the capacitor 47 that is provided in parallelto the battery module 30 is connected to the input and output circuit 43and electric power is input and output. The sweep unit 50 of the sweepmodule 20 connects the battery module 30 to the main line 7 while thegate signal GS is in the ON state. On the other hand, a battery module30 of a sweep module 20 in which the first switching element 41 isturned on and the second switching element 42 is turned off isdisconnected from the main line 7. The sweep unit 50 disconnects thebattery module 30 from the main line 7 while the gate signal GS is inthe OFF state.

When the first switching element 41 and the second switching element 42are simultaneously turned on, a short-circuit occurs. Accordingly, whenthe first switching element 41 and the second switching element 42 aredriven to switch, the sweep unit 50 switches one element from ON to OFFand switches the other element from OFF to ON after a slightly waitingtime has elapsed thereafter. As a result, it is possible to prevent ashort-circuit from occurring.

A VH command value which is instructed by a VH command signal is definedas VH_com, a voltage of each battery module 30 is defined as Vmod, andthe number of sweep modules 20 which are to perform the sweep operation(that is, the number of sweep modules 20 which are to be connected tothe main line 7 in sweep control) is defined as P. In this case, a dutyratio of an ON time to the period T in a gate signal GS is calculated asVH_com/(Vmod×P). In the example illustrated in FIG. 3, the duty ratio ofthe gate signal GS is about 0.46. Strictly, the duty ratio varies due toan influence of the waiting time for preventing occurrence of ashort-circuit. Accordingly, the sweep unit 50 may perform correction ofthe duty ratio using a feedback process or a feedforward process.

As illustrated in FIG. 3, when sweep control is started, first, one of Psweep modules 20 (the sweep module 20 of No. 1 which is furthestupstream in the example illustrated in FIG. 3) is connected. Thereafter,when the delay time DL elapses, a next sweep module 20 (the sweep module20 of No. 2 which is located the second from upstream in the exampleillustrated in FIG. 3) is connected. In this state, the voltage VH whichis output to the power distribution device 5 is a sum value of thevoltages of two sweep modules 20 and does not reach the VH commandvalue. When the delay time DL elapses additionally, the sweep module 20of No. 3 is connected. In this state, the number of sweep modules 20connected to the main line 7 is three of Nos. 1 to 3. Accordingly, thevoltage VH which is output to the power distribution device 5 is a sumvalue of the voltages of three sweep modules 20 and is greater than theVH command value. Thereafter, when the sweep module 20 of No. 1 isdisconnected from the main line 7, the voltage VH returns to the sumvalue of the voltages of two sweep modules 20. When the delay time DLelapses after the sweep module of No. 3 has been connected, the sweepmodule 20 of No. 4 is connected. As a result, the number of sweepmodules 20 which are connected to the main line 7 through sweepcontrolare three of Nos. 2 to 4. As described above, m (three in FIG. 3)sweep modules 20 which are connected to the main line 7 out of M (fivein FIG. 3) sweep modules 20 are sequentially switched.

As illustrated in FIG. 3, the VH command value may not be indivisible bythe voltage Vmod of each battery module 30. In this case, the voltage VHwhich is output to the power distribution device 5 varies. However, thevoltage VH is equalized by the RLC filter and is output to the powerdistribution device 5. Even when the battery modules 30 of the sweepmodules 20 are charged with electric power which is input from the powerdistribution device 5, the connection states of the sweep modules 20 arecontrolled similarly to the timing chart illustrated in FIG. 3.

<Forcible Through Operation>

Control when certain sweep modules 20 are caused to perform a forciblethrough operation and the other sweep modules 20 are caused to perform asweep operation will be described below with reference to FIG. 4. Asdescribed above, the sweep module 20 which has been instructed toperform a forcible through operation maintains a state in which thebattery module 30 is disconnected from the main line 7. The exampleillustrated in FIG. 4 is different from the example illustrated in FIG.3 in that the sweep module 20 of No. 2 is caused to perform a forciblethrough operation. That is, in the example illustrated in FIG. 4, thenumber P of sweep modules 20 which are caused to perform a sweepoperation (that is, the number of sweep modules 20 which are to beconnected to the main line 7) out of five sweep modules 20 included inone string 10 is four. The VH command value, the voltage Vmod of eachbattery module 30, and the delay time DL are the same as in the exampleillustrated in FIG. 3. In the example illustrated in FIG. 4, the periodT of the gate signal GS is “2.4 μsec×4=9.6 μsec.” The duty ratio of thegate signal GS is about 0.58.

As illustrated in FIG. 4, when certain sweep modules 20 (the sweepmodule 20 of No. 2 in FIG. 4) are caused to perform a forcible throughoperation, the number P of sweep modules 20 which are caused to performa sweep operation is less than that in the example illustrated in FIG.3. However, the string 10 adjusts the period T of the gate signal GS andthe duty ratio of the gate signal GS with the decrease in the number Pof sweep modules 20 which are caused to perform a sweep operation. As aresult, the waveform of the voltage VH which is output to the powerdistribution device 5 is the same as the waveform of the voltage VHillustrated in FIG. 3. Accordingly, the string 10 can appropriatelyoutput the commanded voltage VH to the power distribution device 5 evenwhen the number P of sweep modules 20 which are caused to perform asweep operation is increased or decreased.

For example, when a defect (for example, deterioration or failure)occurs in a battery 31 in a certain sweep module 20, the string 10 cancause the sweep module 20 including the battery 31 in which a defect hasoccurred to perform a forcible through operation. Accordingly, thestring 10 can appropriately output the commanded voltage VH to the powerdistribution device 5 using the sweep modules 20 in which a defect hasnot occurred. An operator can replace the battery module 30 includingthe battery 31 in which a defect has occurred (that is, the batterymodule 30 of the sweep module 20 which is performing a forcible throughoperation) in a state in which the string 10 is operating normally. Inother words, in the power supply system 1 according to this embodiment,it is not necessary to stop the operation of the string 10 as a wholewhen a battery module 30 is replaced.

When a certain sweep module 20 is caused to perform a forcibleconnection operation, the connection state of the sweep module 20 whichis caused to perform a forcible connection operation is a normallyconnected state. For example, when the sweep module 20 of No. 2 in FIG.4 is caused to perform a forcible connection operation instead of aforcible through operation, the connection state of No. 2 is maintainedin a “connected state” instead of a “disconnected state.”

When the power supply system 1 includes a plurality of strings 10, theabove-mentioned sweep control is executed in each of the plurality ofstrings 10. The controller (the GCU 2 in this embodiment) thatcomprehensively controls the power supply system 1 as a whole controlsthe operations of the plurality of strings 10 such that a command fromthe host system 6 is satisfied. For example, when a VH command valuerequired from the host system 6 cannot be satisfied by only one string10, the GCU 2 may satisfy the VH command value by causing the pluralityof strings 10 to output electric power.

<String>

The entire configurations of the string 10 and the power supply system 1will be described below in detail with reference to FIG. 1. As describedabove, the string 10 includes an SCU 11 and a plurality of sweep modules20 that is connected in series to the main line 7 with a power circuitmodule 40 interposed therebetween. The main line 7 of the string 10 isconnected to a bus line 9 extending from the power distribution device5. The string 10 includes a bus line voltage detecting unit 21, a systembreaker (this system breaker is appropriately referred to as a “systemmain relay (SMR)”) 22, a string capacitor 23, a string current detectingunit 24, a string reactor 25, and a string voltage detecting unit 26sequentially from the power distribution device 5 side (upstream) in themain line 7. Disposition of certain members may be modified. Forexample, the system breaker 22 may be provided downstream from thestring capacitor 23.

The bus line voltage detecting unit 21 detects a voltage of the bus line9 extending from the power distribution device 5 to the string 10. Thesystem breaker 22 switches between connection and disconnection betweenthe string 10 and the power distribution device 5. In this embodiment,the system breaker 22 is driven in accordance with a signal which isinput from the SCU 11. The string capacitor 23 and the string reactor 25form an RLC filter to achieve equalization of a current. The stringcurrent detecting unit 24 detects a current flowing between the string10 and the power distribution device 5. The string voltage detectingunit 26 detects a total voltage of voltages of the plurality of sweepmodules 20 which is connected in series to the main line 7 in the string10, that is, a string voltage of the string 10.

In the example illustrated in FIG. 1, the system breaker 22 includes aswitch 22 a and a fuse 22 b. The switch 22 a is a device that connectsor disconnects the string 10 to and from the power distribution device5. The switch 22 a can be appropriately referred to as a string switch.By turning on the switch 22 a, the main line 7 of the string 10 isconnected to the bus line 9 of the power distribution device 5. Byturning off the switch 22 a, the string 10 is disconnected from thepower distribution device 5. The switch 22 a is controlled by the SCU 11controlling the string 10. By operating the switch 22 a, the string 10can be appropriately disconnected from or connected to the powerdistribution device 5. The fuse 22 b is a device that stops anunexpected large current when the large current flows in the main line 7of the string 10 in view of design of the string 10. The fuse 22 b isalso appropriately referred to as a string fuse.

Here, when batteries incorporated into one battery module 30 have thesame standard, the voltage of one battery module 30 increases as thenumber of batteries incorporated increases. On the other hand, when thevoltage of one battery module 30 is high, the battery module isdangerous for an operator to handle and is heavy. In this regard, asmany batteries as possible may be be incorporated into one batterymodule 30 within a range of a voltage with which an operator will not besubjected to a significant accident even with touch of the operator withthe fully charged battery module (for example, lower than 60 V andpreferably lower than 42 V) and within a range of a weight with which anoperator can easily replace the battery module. The battery module 30which is incorporated into the string 10 does not need to include thesame batteries, and the number of batteries which are incorporated intoone battery module 30 can be determined depending on types, standards,or the like of the batteries which are incorporated into the batterymodule 30. The string 10 is configured to output a necessary voltage bycombining sweep modules 20 into which the battery module 30 has beenincorporated in series. The power supply system 1 is configured tooutput electric power required for connection to the power system 8 bycombining a plurality of strings 10.

In this embodiment, the power distribution device 5 to which a pluralityof strings 10 of the power supply system 1 is connected includes subpower distribution devices 5A and 5B that are connected to the strings10A and 10B. The strings 10A and 10B connected to the sub powerdistribution devices 5A and 5B are connected in parallel via the subpower distribution devices 5A and 5B. The power distribution device 5controls distribution of electric power which is input to the strings10A and 10B from the power system 8, combination of electric power whichis output from the strings 10A and 10B to the power system 8, and thelike through the sub power distribution devices 5A and 5B connected tothe strings 10. The power distribution device 5 and the sub powerdistribution devices 5A and 5B are controlled such that the power supplysystem 1 into which a plurality of strings 10 is incorporated serves asa single power supply device as a whole by cooperation between the GCU 2connected to the host system 6 and the SCU 11 that controls each string10.

For example, in this embodiment, a downstream side from the powerdistribution device 5, that is, the strings 10A and 10B side, iscontrolled with a direct current. An upstream side from the powerdistribution device 5, that is, the power system 8, is controlled withan alternating current. The voltages of the strings 10A and 10B arecontrolled to be roughly balanced with the voltage of the power system 8via the power distribution device 5. When the voltage of each of thestrings 10A and 10B is controlled to be lower than that of the powersystem 8, a current flows from the power system 8 to each of the strings10A and 10B. At this time, when sweep control is executed in the strings10A and 10B, the battery modules 30 are appropriately charged. When thevoltage of each of the strings 10A and 10B is controlled to be higherthan that of the power system 8, a current flows from each of thestrings 10A and 10B to the power system 8. At this time, when sweepcontrol is executed in the strings 10A and 10B, the battery modules 30are appropriately discharged. The power distribution device 5 maymaintain the voltages of the strings 10A and 10B to be equal to thevoltage of the power system 8 such that a current hardly flows in thestrings 10A and 10B. In this embodiment, this control can be executedfor each of the sub power distribution devices 5A and 5B to which thestrings 10A and 10B are connected. For example, by adjusting the voltagefor each of the strings 10A and 10B, control may be executed such that acurrent hardly flows in certain string 10 out of a plurality of strings10A and 10B connected to the power distribution device 5.

In the power supply system 1, the total capacity of the power supplysystem 1 can be increased by increasing the number of strings 10 whichare connected in parallel to the power distribution device 5. Forexample, with the power supply system 1, it is possible to construct alarge system that can output electric power such that a sudden increasein demand in the power system 8 can be absorbed or can supplement suddenpower shortage in the power system 8. For example, by increasing thecapacity of the power supply system 1, great surplus electric power ofthe power system 8 can be appropriately transferred to charging of thepower supply system 1. For example, when output power of a power plantis surplus in a night time zone in which demand for electric power islow or when an amount of electric power generated in a largephotovoltaic system increases suddenly, the power supply system 1 canabsorb surplus electric power via the power distribution device 5. Onthe other hand, when demand for electric power in the power system 8increases suddenly, necessary electric power can be appropriately outputfrom the power supply system 1 to the power system 8 via the powerdistribution device 5 in accordance with a command from the host system6. Accordingly, with the power supply system 1, power shortage in thepower system 8 is appropriately supplemented.

In the power supply system 1, it is not necessary to normally connectall battery modules 30 out of a plurality of battery modules 30 which isincorporated into a string 10. Since a forcible through operation can beperformed for each battery module 30 as described above, a batterymodule 30 in which a defect has occurred can be disconnected from sweepcontrol of the string 10 when a defect has occurred in the batterymodule 30. Accordingly, in the power supply system 1, a battery which isused for the battery module 30 does not need to be a new battery whichhas not been used.

For example, a secondary battery which has been used as a driving powersource of a motor-driven vehicle such as a hybrid vehicle or an electricvehicle can be appropriately reused. Even when such a secondary batterywhich has been used as a driving power source is used, for example, forabout 10 years, the secondary battery can satisfactorily perform asecondary battery function. In the power supply system 1, since abattery module 30 in which a defect has occurred can be immediatelydisconnected, a battery can be incorporated into the battery module 30,for example, by ascertaining that the battery performs a necessaryfunction. The time for sequentially recovering a secondary battery whichhas been used as a driving power source of a motor-driven vehicle comesup. With the power supply system 1, for example, secondary batteriescorresponding to 10,000 motor-driven vehicles may be incorporatedthereinto and thus considerable recovered secondary batteries can beabsorbed. It cannot be seen when a secondary battery which has been usedas a driving power source of a motor-driven vehicle deteriorates inperformance. When such a secondary battery is reused for a batterymodule 30 of the power supply system 1, it is not possible to predictwhen a defect occurs in the battery module 30.

With the power supply system 1 which has been proposed herein, it ispossible to appropriately disconnect a battery module 30 via a sweepmodule 20. Accordingly, even when a defect occurs suddenly in a batterymodule 30 or a secondary battery incorporated into the battery module30, it is not necessary to stop the power supply system 1 as a whole.

The plurality of strings 10 of the power supply system 1 is connected inparallel to the power distribution device 5 which is connected to thepower system 8 as described above. Electric power which is input oroutput between the power system 8 and the power distribution device 5can be determined by the host system 6 that controls the power system 8.For example, the GCU 2 that takes charge of certain or all of thefunctions of the control device 100 can calculate a predicted value of acurrent value flowing in the strings 10 to which electric power isdistributed by the power distribution device 5 depending on electricpower which is input or output to and from the power system 8 and thenumber of strings 10 to which electric power is distributed. Forexample, the electric power (input or output) requested for the powerdistribution device 5 from the power system 8 is determined by the hostsystem 6.

The host system 6 requests the power distribution device 5 to input oroutput necessary electric power via the GCU 2. For example, when thereis surplus electric power in the power system 8, the host system 6requests the power distribution device 5 to take electric power from thepower system 8. In response to this request, the power distributiondevice 5 controls the voltage of the string 10 side such that thisvoltage is lower than that on the power system 8 side. When there is ashortage of electric power in the power system 8, the host system 6requests the power distribution device 5 to supply electric power to thepower system 8. In response to this request, the power distributiondevice 5 controls the voltage of the string 10 side such that thisvoltage is higher than that on the power system 8 side.

At this time, states of the string 10, the battery module 30, the powercircuit module 40, and the like are normally monitored based on measuredvalues which are detected by the string current detecting unit 24 andthe string voltage detecting unit 26 which are provided in the main line7 of the string 10, the voltage detecting unit 35 and the temperaturedetecting unit 36 which are provided in the battery module 30, thetemperature detecting unit 48 which is provided in the power circuitmodule 40, and the like. In a device that detects states of the powersupply system 1 based on a current value, an error increases as thecurrent value decreases.

In the power supply system 1, the inventor has been aware of knowledgethat in particular a decrease in a current flowing in the main line 7, acurrent flowing in the input and output circuit 43 of the power circuitmodule 40, or the like causes misunderstanding of the states of thepower supply system 1. For example, as described above, when a pluralityof strings 10 is connected in parallel to the power distribution device5 and an amount of electric power requested from the power distributiondevice 5 is small, the current flowing in the main line 7 of one string10 is decreased, for example, by uniformly distributing the current tothe plurality of strings 10 connected in parallel from the powerdistribution device 5. When the current flowing in the main line 7 ofthe string 10 decreases, an error in the detected current value in thedevice that detects states of the string 10 based on a current valueincreases, which may cause misunderstanding of the states of the strings10.

FIG. 5 is a block diagram illustrating the control device 100 of thepower supply system 1. From the above-mentioned point of view, thecontrol device 100 of the power supply system 1 has only to include afirst processing unit 101 and a second processing unit 102 asillustrated in FIG. 5.

Here, the control device 100 can be a device that controls inputting ofelectric power from the power system 8 to a plurality of strings 10connected to the power distribution device 5 and outputting of electricpower form the plurality of strings 10 to the power system 8. In theabove-mentioned embodiment, for example, control of the control device100 can be taken charge of in cooperation by the GCU 2 serving as apower controller that controls the power distribution device 5 or thestrings 10, the SCU 11, the sweep units 50, and the like. For example,the control device 100 controls the power distribution device 5 or thestrings 10 based on a relationship with the situation of the powersystem 8 or the like in accordance with a command from the host system6. A variety of information which is detected in the power supply system1 can be managed by an external server which is located remotely by IOTtechnology. Various processes of the control device 100 can be remotelycontrolled in cooperation with an external manager computer which isaccessibly connected to the power supply system 1 via a communicationnetwork by cloud computing technology.

The first processing unit 101 is a processing unit that performs a firstprocess of determining certain strings 10 out of a plurality of strings10 connected in parallel to the power distribution device 5. The secondprocessing unit 102 is a processing unit that performs a second processof performing inputting of electric power to the plurality of strings 10connected in parallel to the power distribution device 5 or outputtingof electric power from the plurality of strings 10 to the powerdistribution device 5 using at least certain strings 10 which aredetermined by the first processing unit 101.

In this case, at least electric power is distributed to certain strings10 which are determined by the first processing unit 101 from the powerdistribution device 5. Accordingly, in the certain strings 10, electricpower which is distributed from the power distribution device 5 isstabilized. Accordingly, in the certain strings 10, a current flowing inthe main line 7 of the string 10 is likely to be stabilized in a statein which a necessary power value is secured. Accordingly, in the devicethat detects states of the string 10 based on a current value, an errorof the detected current value is curbed and the state of the string 10is likely to be appropriately and easily understood. In the certainstrings 10, it is possible to stably drive the power supply system 1.

For example, the power distribution device 5 may evaluate performance ofthe strings 10 connected in parallel in advance and the first processingunit 101 may be configured to determine the strings 10 to which electricpower is to be distributed based on the result of performanceevaluation. For example, the first processing unit 101 may be configuredto select the strings 10 with good performance as the certain strings 10based on the result of performance evaluation. In this case, when thepower distribution device 5 is requested to stably input or outputelectric power from the host system 6, it is possible to obtain stableperformance. The first processing unit 101 may be configured to selectstrings 10 with poor performance as the certain strings 10. In thiscase, for example, a predetermined inspection mode may be executed toinspect the battery module 30 of each sweep module 20 in the string 10.A predetermined deterioration recovery mode may be executed to recoverdeterioration of the battery module 30 of each sweep module 20. The modein which the strings 10 with poor performance are selected as thecertain strings 10 can be executed, for example, when a request from thehost system 6 to the power distribution device 5 (for example, a requestfor input or output of electric power) is not strict.

For example, the second process which is performed by the secondprocessing unit 102 is advantageous when electric power input or outputbetween the power distribution device 5 and a plurality of strings 10 isequally distributed to the plurality of strings 10 and a predeterminedcurrent value is not obtained in certain strings 10. In this case, thesecond processing unit 102 can be configured to distribute electricpower for obtaining a predetermined current value in certain strings 10to the certain strings. The second processing unit 102 may be configuredto distribute surplus electric power to at least one string other thanthe certain strings determined by the first processing unit 101 out ofthe plurality of strings 10. Accordingly, a predetermined current valueis stably obtained in certain strings 10 determined by the firstprocessing unit 101. With the certain strings 10, the power supplysystem 1 can be stably driven. Since surplus electric power can betransferred to other strings 10, other strings 10 can be appropriatelyutilized effectively.

In this case, first, the second processing unit 102 can perform aprocess of obtaining a current value of the main line 7 of each string10 when electric power input or output between the power distributiondevice 5 and the plurality of strings 10 is equally distributed to theplurality of strings 10. Then, the process of determining whether theobtained current value of the main line 7 of each string 10 reaches thepredetermined current value can be performed in each string 10. When itis determined that the predetermined current value is not obtained incertain strings 10 determined by the first processing unit 101, electricpower for obtaining the predetermined current value in the certainstrings 10 is calculated. Then, the power distribution device 5 iscontrolled such that the calculated electric power is distributed to thecertain strings 10. The power distribution device 5 can be configured toadditionally distribute surplus electric power to at least one string 10other than the certain strings 10 determined by the first processingunit 101 out of the plurality of strings 10 connected in parallel to thepower distribution device 5.

Here, the predetermined current value is merely, for example, a currentvalue required for accurately detecting a state of a string 10. Thepredetermined current value can be determined, for example, for eachstring 10 connected to the power distribution device 5. In this case,the predetermined current value may be determined depending on a batterymodule 30 attached to the string 10 or a battery 31 (see FIG. 2)incorporated into the battery module 30. The control device 100 caninclude a storage unit that stores the predetermined current value foreach string 10. The current value which is determined for each string 10may be appropriately edited. The current value which is determined foreach string 10 may be appropriately calculated from an evaluation valuefor performance of the string 10, for example, by the control device100.

The second processing unit 102 may be configured to distribute electricpower to at least one string 10 of the certain strings 10 when electricpower input or output between the power distribution device 5 and aplurality of strings 10 is distributed to the certain strings 10 and thepredetermined current value is not obtained in at least one of thecertain strings 10.

For example, when electric power is distributed to certain strings 10determined by the first processing unit 101 and input or output electricpower which is requested to the power distribution device 5 from thehost system 6 is small, the current value in the certain strings 10 towhich electric power is distributed may be small. For example, thepredetermined current value may not be obtained in certain strings 10out of the certain strings 10 determined by the first processing unit101. In this case, the second processing unit 102 can be configured todistribute electric power to at least one string 10 of the certainstrings 10. Accordingly, the current value in the string 10 to whichelectric power is distributed is likely to be stabilized.

FIG. 6 is a flowchart illustrating an example of the first process andthe second process in the control device 100. As illustrated in FIG. 6,in the first process, certain strings 10 out of a plurality of strings10 connected in parallel to the power distribution device 5 aredetermined (S11). In the second process, for example, a current value A1flowing in each string 10 when electric power is distributed to thecertain strings 10 determined in the first process is calculated (S12).It is determined whether the calculated current value A1 is equal to orgreater than a predetermined current value A0 of each string 10 (A1>A0)(S13). When it is determined in the process (S13) that the calculatedcurrent value A1 is equal to or greater than the predetermined currentvalue A0 of each string 10 (YES), electric power is distributed to thecertain strings 10 determined in the first process (S14).

When it is determined in the process (S13) that the calculated currentvalue A1 does not satisfy the predetermined current value A0 of eachstring 10 (NO), certain strings 10 can be additionally determined out ofthe certain strings 10 determined in the first process (S11). That is,certain strings 10 are redetermined (S15). This redetermination may beperformed, for example, by the function of the first processing unit101. Then, a current value A2 flowing in each string 10 when electricpower is distributed to certain strings 10 which are redetermined iscalculated (S16). It is determined whether the calculated current valueA2 is equal to or greater than the predetermined current value A0 ofeach string 10 (A2>A0) (S17). When it is determined that the calculatedcurrent value A2 is equal to or greater than the predetermined currentvalue A0 of each string 10 (YES), electric power is distributed to thecertain strings 10 redetermined in the process of S15 in the secondprocess by the second processing unit 102 (S18).

When it is determined in the process (S17) that the calculated currentvalue A2 does not satisfy the predetermined current value A0 of eachstring 10 (NO), certain strings 10 are additionally redetermined out ofthe certain strings 10 (S15). The processes from redetermination (S15)to determination (S17) are repeated until the calculated current valueA2 becomes equal to or greater than the predetermined current value A0of each string 10 (A2>A0).

According to the second process, when electric power is distributed tothe determined certain strings 10, the current values A1 and A2 flowingin each string 10 becomes equal to or greater than the predeterminedcurrent value A0 of each string 10. Accordingly, it is possible tostably secure a current value required for a string 10.

For example, electric power which is output from the power system 8 to aplurality of strings 10 connected to the power distribution device 5 canbe calculated in accordance with a command from the host system 6 or theGCU 2. Even when electric power which is calculated in accordance with acommand from the host system 6 or the GCU 2 varies, the current valuerequired for a string 10 is stably secured through the first process andthe second process which are performed by the control device 100. Sincethe current value required for each string 10 is stably secured, it ispossible to accurately monitor the state of each string 10 and to stablyoperate the power supply system 1.

In the processes from redetermination (S15) to determination (S17), whendetermination of whether the calculated current value A2 is equal to orgreater than the predetermined current value A0 of each string 10(A2>A0) is repeatedly performed, the number of strings 10 which aredetermined as certain strings 10 in the redetermination (S15) decreasesgradually. Finally, it is conceivable that the number of strings 10 beone. When the calculated current value is not equal to or greater thanthe predetermined current value of each string 10 even if any string 10is selected in the processes from the redetermination (S15) to thedetermination (S17), this can be fed back to the host system 6. Untilelectric power requested from the host system 6 to the powerdistribution device 5 increases stably, the strings 10 connected to thepower distribution device 5 may be paused.

The power supply system has been described above in various forms.Unless otherwise mentioned, examples or the like of the power supplysystem according to the embodiment do not limit the disclosure. Thepower supply system can be modified in various forms and the elements orprocesses mentioned herein can be appropriately omitted or appropriatelycombined unless any particular problem is caused.

What is claimed is:
 1. A power supply system comprising: a powerdistribution device that is connected to a power system; a plurality ofstrings that is connected to the power distribution device in parallelwith each other; and a control device, wherein each string includes amain line that is connected to the power distribution device, and aplurality of sweep modules that is disposed along the main line, whereineach sweep module includes a battery module, an input and output circuitthat is configured to connect the battery module in series to the mainline, and at least one switching element that is provided in the inputand output circuit and is configured to switch between connection anddisconnection between the battery module and the main line, wherein thecontrol device is configured to control inputting of electric power fromthe power system connected to the power distribution device to theplurality of strings connected to the power distribution device andoutputting of electric power from the plurality of strings to the powersystem, and wherein the control device is configured to perform a firstprocess of determining certain strings out of the plurality of stringsconnected in parallel to the power distribution device and a secondprocess of performing inputting of electric power to the plurality ofstrings connected in parallel to the power distribution device oroutputting electric power from the plurality of strings to the powerdistribution device using at least the certain strings.
 2. The powersupply system according to claim 1, wherein the second process includesdistributing electric power for acquiring a predetermined current valuein the certain strings to the certain strings and distributing surpluselectric power to at least one string other than the certain stringsdetermined in the first process out of the plurality of strings whenelectric power input or output between the power distribution device andthe plurality of strings is equally distributed to the plurality ofstrings and the predetermined current value is not acquired in thecertain strings.
 3. The power supply system according to claim 1,wherein the first process includes additionally determining certainstrings out of the certain strings when electric power input or outputbetween the power distribution device and the plurality of strings isdistributed to the certain strings and a predetermined current value isnot acquired in at least one of the certain strings.